1. Technical Field
The present invention relates to wireless communications, and more particularly, to a method of communication using a frame in a wireless communication system.
2. Related Art
The Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, incorporated herein by reference, provides a technique and protocol for supporting broadband wireless access. The standardization had been conducted since 1999 until the IEEE 802.16-2001 (incorporated herein by reference) was approved in 2001. The IEEE 802.16-2001 is based on a physical layer of a single carrier (SC) called ‘WirelessMAN-SC’. The IEEE 802.16a standard (incorporated herein by reference) was approved in 2003. In the IEEE 802.16a standard, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFPMA’ are further added to the physical layer in addition to the ‘WirelessMAN-SC’. After completion of the IEEE 802.16a standard, the revised IEEE 802.16-2004 standard (incorporated herein by reference) was approved in 2004. To correct bugs and errors of the IEEE 802.16-2004 standard, the IEEE 802.16-2004/Cor1 (hereinafter, IEEE 802.16e) was completed in 2005 in a format of ‘corrigendum’ (incorporated herein by reference).
Recently, standardization on the IEEE 802.16m is in progress as a new technical standard based on the IEEE 802.16e (incorporated herein by reference). The IEEE 802.16m (incorporated herein by reference), which is a newly developed technical standard, has to be designed to support the previously designed IEEE 802.16e. That is, a technology (i.e., IEEE 802.16m) of a newly designed system has to be configured to operate by effectively Incorporating a conventional technology (i.e., IEEE 802.16e). This is called backward compatibility. The backward compatibility considered in the design of IEEE 802.16m is as follows.
First, a user equipment (UE) employing a new technology has to operate with the same performance as a base station (BS) (or a UE) employing a conventional technology. Hereinafter, for simplicity, any system (e.g., UE, BS, etc.) employing the new technology is referred to as a new system, and any system (e.g., UE, BS, etc.) employing the conventional technology is referred to as a legacy system. Second, the new system has to operate in the same radio frequency (RF) subcarrier and the same bandwidth as those of the legacy system. Third, the new BS has to support a case where the new UE and the legacy UE coexist in the same RF subcarrier, and overall system performance has to be improved by a ratio of the new UE. Fourth, the new BS has to support a handover of the legacy UE and a handover of the new UE such that their handover performances conform to those of legacy BSs. Fifth, the new BS has to support both the new UE and the legacy UE to the same level as that supported by the legacy BS to the legacy UE.
The new BS performs scheduling on radio resources to be allocated to the legacy UE or the new UE within a bandwidth that can be supported by the new BS. Scheduling of the radio resources can be performed in a logical frame consisting of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and a plurality of subchannels in a frequency domain. Therefore, there is ongoing research on a frame structure in which the IEEE 802.16m system can support backward compatibility with the IEEE 802.16e system.
In particular, in a case where time division duplexing (TDD)-type frame structures having different cyclic prefix (CP) lengths coexist in neighbor cells, a boundary between downlink and uplink regions may overlap, which may result in mutual interference. Accordingly, there is a need to design a TDD frame structure capable of preventing interference between the TDD frame structures coexisting in the adjacent cells.
In addition, although a system profile based on the conventional IEEE 802.16 standard supports only a TDD scheme, there is an attempt to also support a frequency division duplexing (FDD) scheme in which uplink transmission and downlink transmission are performed in different frequency bands. Accordingly, for convenience of system design and hardware sharing, there is a need to design an FDD frame structure having a common feature with the TDD frame structure.